<?php
$zip = new ZipArchive;
$res = $zip->open('test.zip', ZipArchive::CREATE);
if ($res === TRUE) {
    $zip->addFromString('dir/test.txt', 'Type here the content-you want to add');
    $zip->close();
    echo 'Content added to Zip successfully';
} else {
    echo 'Failed to Add';
}
?>